Basically, in a nutshell. If your bike is stiffened in the compression, your goal is to keep your forks up in the stroke. If you are too deep into the stroke, there is harshness over braking and studder bumps. Meaning, if you have your forks set as soft as they go, your forks will be more towards the middle of the stroke, and not the top. The deeper into the travel you go, the harder the valving is. When you stiffen the forks up, it lets you utilize the initial part of your fork movement. That is the reason many of us prefer stiffer springs. It isn't to help you from bottoming usually. It is to keep you up higher for cornering, braking bumps, during braking etc.